A Brief Review for Clinicians of Iron Metabolism and the Safety, Efficacy, and Rationale for Use of Intravenous Iron Products

Abstract

Iron is an abundant element that is essential for multiple biologic processes. Iron metabolism is not entirely understood, but since the discovery of hepcidin, much progress has been made especially in the last five years. This article is intended to enhance clinician understanding of iron metabolism which may inform decisions about parenteral iron use in iron-restricted erythropoiesis (IResE). This article briefly discusses intravenous (IV) iron utilization in iron deficiency, anemia of chronic inflammation (ACI), functional iron deficiency (FID), and anemia associated with chronic kidney disease, heart failure, pregnancy, inflammatory bowel disease and cancer. Oral iron therapy is valuable in mild to moderate pure iron deficiency. Intravenous iron is required when a prompt response is needed in severe pure iron deficiency. ACI is a hypoferremic state resulting from altered iron metabolism. In ACI, IV iron is needed to overcome the blocking effects of hepcidin on intestinal absorption. ESAs stimulate erythropoiesis increasing iron utilization. This surge in iron requirement can result in FID, especially when ESAs are used in patients with ACI. Intravenous iron is required to treat or avoid iron deficiency in FID when inflammation is present. Parenteral iron maximizes ESA response and can make using erythropoiesis-stimulating agents (ESAs) safer by being ESA sparing. The complex and seemingly ubiquitous nature of iron in humans and the inadequate methods of assessment of iron status in inflammatory states means clinical and laboratory monitoring and individualization of care remain essential. The decision to administer intravenous iron is complex as it often lacks robust consensus guidelines; despite this we can expect utilization of these products to increase as they are safe, effective and necessary.